How Coffee MK & Microwave Work

How Coffee Makers WorkMost people who are dependent on caffeine have breakfast with an old friend - the coffeemaker! Every morning you scoop in the coffee, add the water and turn it on, but have youever wondered what is happening inside? How does the water get from the liftlecompartment where you pour it in to the top of the coffee maker, and what is that gurglingsound?

In this article, we will look inside a typical drip coffee maker so you can understand exactlywhat is happening when you make coffee. We will also look at the possible problems thatmight cause your coffee maker to stop working. By the end of this article, you may look atyour old friend in a completely new wayl

At a GlanceA modern drip coffee maker is a surprisingly simple device. Manufacturers have had 25years to hone their designs, so these coffee makers are pretty straightforward once you openthem up. Here is the coffee maker that we will be examining for this article:Now let's take a look inside.lnside a Coffee Makerlf you take off the top of the coffee maker, you find three things:There is a little bucket that holds the water when you pour it into the pot at the start

of the coffee-making cycle (on the right in the

pic{ure

above). There is a hole in the

bottom of the bucket, and its role will become obvious in a moment.

There is a black tube that canies the hot water to the drip area.

There is the drip area (on the left-hand side of this picture). Water arrives here from

the black hot-water tube and simply falls through the holes into the coffee

grounds.

Looking at this picture, you get your first impression that this isn't a high-tech device. lf youtake the bottom offthe coffee maker, here is what you will find:

The depression on the right-hand side of this figure is the bottom ofthe bucket. The orange

tube in the center is the hol-water tube (it connects to the black tube that we saw in the

previous picture). The other orange tube picks

up cold water from the hole in the bucket. You

can also see the power cord coming in as well as lhe switch that turns the coffee maker on

and off.The heating element is an aluminum extrusion with two parts: a resistive heating element

and a tube for water to flow through, like this:

The Heating ElementThe resistive heating element is simply a coiled wire, very similar to the filament of a lightbulb or the element in an electric toasier, that gets hot when you run electricity through it. Ina resistive element like this, the coil is embedded in a plaster to make it more rugged. Theheating element has two jobs:

1 . \Nhen you first put the water in the coffee maker, the heating element boils it.2. Once the coffee is made, the heating element keeps the cofiee warm.

In the following

pictures, you

can see the connection between the heating element and the

warming plate. The heating element presses direc.tly against the underside of the warming

plate, and a white, heat-conductive grraae makes sure that the heat transfers efiicienfly to

the plate. This grease, by the way, is extremely messy (very hard to get off of your fingers!).

You find this grease in all sorls of devices, including stereo amplifiers, power

supplies--

pretty much anything that has to dissipate heat.The coffee maker's switch turns power to the heating element on and ofi. To keep thehealing element from overheating, there are three solid€tate temperature sensors, asshown here:

temporltur9 t€naonlThe device attached direc-tly to the coil is the primary temperature sensor. \Men it detects

the coil getting too hot, it cuts off the current. Then, when it cools down, it turns the coil backon. By cycling on and off like this, it keeps the coil at an even temperature. The other twodevices appear to be thermal fuses. They simply cut power if they sense too high atemperature. They are there for safety reasons, in the event that the main sensor fails.One part that is not visible in this coffee maker is a one-way valve. This valve is either in the

hole in the bucket or in the aluminum heating pipe. lf there were no one-way valve, then theboiling water would be just as likely to flow back into the bucket as to rise up the black tube.The one-way valve lets cold water into the aluminum tube, but forces the bubbles of boilingwater to flow up the black tube. lf you blow on the tube leading into this value, the valveshould be open. lf you inhale through the tube, the one-way valve should block any air.